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Abstract

During the blood stages of malaria, several hundred parasite-encoded proteins are exported beyond the double-membrane barrier that separates the parasite from the host cell cytosol1,2,3,4,5,6. These proteins have a variety of roles that are essential to virulence or parasite growth7. There is keen interest in understanding how proteins are exported and whether common machineries are involved in trafficking the different classes of exported proteins8,9. One potential trafficking machine is a protein complex known as the Plasmodium translocon of exported proteins (PTEX)10. Although PTEX has been linked to the export of one class of exported proteins10,11, there has been no direct evidence for its role and scope in protein translocation. Here we show, through the generation of two parasite lines defective for essential PTEX components (HSP101 or PTEX150), and analysis of a line lacking the non-essential component TRX2 (ref. 12), greatly reduced trafficking of all classes of exported proteins beyond the double membrane barrier enveloping the parasite. This includes proteins containing the PEXEL motif (RxLxE/Q/D)1,2 and PEXEL-negative exported proteins (PNEPs)6. Moreover, the export of proteins destined for expression on the infected erythrocyte surface, including the major virulence factor PfEMP1 in Plasmodium falciparum, was significantly reduced in PTEX knockdown parasites. PTEX function was also essential for blood-stage growth, because even a modest knockdown of PTEX components had a strong effect on the parasite’s capacity to complete the erythrocytic cycle both in vitro and in vivo. Hence, as the only known nexus for protein export in Plasmodium parasites, and an essential enzymic machine, PTEX is a prime drug target.

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Acknowledgements

We thank T. Templeton, B. Franke-Fayard, C. Janse, A. Cowman, J. Boddey, B. Cooke, M. Duffy, L. Tilley, R. Anders, F. Fowkes, A. McLean and D. Bursac for reagents and/or other assistance with aspects of this study; D. Stanisic, F. Baiwog and I. Mueller for contributions to clinical studies of pregnant women; and P. Siba. We also thank the Australian Red Cross Blood Bank for the provision of human blood and serum. This work was supported by grants from the National Health and Medical Research Council (NHMRC) of Australia (1021560, 1025665 and 637406) and the Victorian State Government Operational Infrastructure Support Scheme. T.F.d.K.-W. is an NHMRC Career Development Fellow, and J.G.B. is a NHMRC Senior Research Fellow. B.E. and K.M. are the recipients of Australian Postgraduate Awards.

Author information

Author notes

    • Brendan Elsworth
    • , Kathryn Matthews
    • , Brendan S. Crabb
    • , Paul R. Gilson
    •  & Tania F. de Koning-Ward

    These authors contributed equally to this work.

Affiliations

  1. Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, 3004, Australia

    • Brendan Elsworth
    • , Catherine Q. Nie
    • , Sarah C. Charnaud
    • , Paul R. Sanders
    • , Jo-Anne Chan
    • , Mauro F. Azevedo
    • , James G. Beeson
    • , Brendan S. Crabb
    •  & Paul R. Gilson
  2. Monash University, Clayton, Victoria, 3800, Australia

    • Brendan Elsworth
    • , Sarah C. Charnaud
    • , James G. Beeson
    • , Brendan S. Crabb
    •  & Paul R. Gilson
  3. Deakin University, Waurn Ponds, 3216, Australia

    • Kathryn Matthews
    • , Ming Kalanon
    • , Scott A. Chisholm
    • , Natalie A. Counihan
    •  & Tania F. de Koning-Ward
  4. National Center for Genetic Engineering and Biotechnology (BIOTEC), Pathum Thani 12120, Thailand

    • Philip J. Shaw
  5. The University of Geneva, 1211 Geneva 4, Switzerland

    • Paco Pino
  6. The University of Melbourne, Parkville, Victoria, 3010 Australia

    • Stephen J. Rogerson
    • , James G. Beeson
    •  & Brendan S. Crabb

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Contributions

B.E., K.M,. P.R.G. and T.F.d.K.-W. designed, performed and interpreted much of the experimental work. B.S.C. designed and interpreted the work and, along with P.R.G. and T.F.d.K.-W., wrote the manuscript. C.Q.N., M.K., S.C.C., P.R.S., S.A.C. and N.A.C. performed experiments and provided intellectual insight into aspects of this study. P.J.S., P.P., J.C., M.F.A., J.G.B. and S.J.R. provided reagents and intellectual input into study design. All authors commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Brendan S. Crabb or Paul R. Gilson or Tania F. de Koning-Ward.

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DOI

https://doi.org/10.1038/nature13555

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